In a multicolor image forming apparatus, such as a color laser printer, a charger is provided for every process cartridge corresponding to each developer color (yellow, magenta, cyan, and black). In this type of image forming apparatus, the following Patent Document 1 discloses that a reduction in the number of parts and miniaturization of the apparatus are achieved by making common a high-voltage power supply unit (voltage application circuit) which applies high voltages to the individual chargers.